Most likely the sail is staysail of some type. Possibly even a wind
seeker for super light air. When trying to use a genoa
, with it's heavy cloth, is futile.
Or perhaps a "tall boy" staysail that's used in conjunction with a spinnaker
. Though the former's more likely, as staysails used with spinnakers are usually set back from the headstay about 30-45% of one's J measurement.
Pics of the gear
, & more description of the sail(s) would help. But other than it possibly being some of the Merriman hardware
already mentioned, it could be some Mariner furling
gear. As I have some of that ancient stuff (Mariner), that's exactly as you describe. Some of which I've used it fly staysails as, well as loose luffed jibs. Think of it as an alternative to a 2nd headstay.
Pretty much, it's the forerunner to this kind of gear Harken
The wire bail which is on the units to connect them to the headstay, is most likely there to stop the drum from rotating. Thus keeping the feeder arm for the line in the proper position.
Though again, without pics...